It is necessary to wear a crash helmet when riding a bicycle or a motorcycle. A ring band is provided in the crash helmet to be located and matched at the brow of a user. If the ring band is not an adjustable structure, it cannot apply to people having different sizes of heads. Several kinds of ring band adjustment structures have been proposed to let ring bands be adjustable.
As shown in FIG. 1, a fixing seat 1 and a cover sheet 2 are provided in a ring band adjustment structure. A pair of adjusters 4 are connected to two end portions of a ring band 3. The fixing seat 1 is a bar-shaped box with two openings 11 and 12 on two side faces thereof to be inserted by two end portions 31 and 32 of the ring band 3, respectively. The end portion 31 of the ring band 3 uses a pair of locating holes 33 to lock a pair of locating posts 41 of one of the adjusters 4. The other end portion 32 of the ring band 3 also uses a pair of locating holes 34 to lock a pair of locating posts 41 of the other adjuster 4. The pair of adjusters 4 respectively have guide posts 42, which protrude into guide grooves 21 and 22 at two sides of the cover sheet 2 covering an opening of the outer surface of the fixing scat 1. An insertion post 44 on an inner face of a joining sheet 43 of the guide post 42 is inserted into a post hole of the guide post 42 for locating.
Each of the adjusters 4 has a slide groove 47 to be extended into by a slide bar 46. The slide bar 46 at each side penetrates into a bottom cavity 13 or 14 of the fixing seat 1. A fixing tooth block 49 of an upper end portion of the slide bar 46 joins a rack 15 or 16 of an inner face of the fixing seat 1. The slide bar 46 has a spring 48 at an inner end portion thereof to contact a bottom face of the slide groove 47. A small shielding sheet 45 is provided outside the slide groove 47. Each of the adjusters 4 has a groove 40 on a back face thereof to be penetrated through by the rack 15 or 16. The cover sheet 2 has a central hole 23 so that a screw 24 can penetrate therethrough to join a screw hole of a central post 17 of the fixing seat 1, thereby completing the whole assembly action.
Although the above prior art has the cover sheet to accommodate the whole adjustment structure, because the fixing seat needs to be fixedly joined with the cover sheet, a joining structure must be provided between them. Because they have the same length and width, some material will be wasted, thus increasing the cost. Moreover, two ends of the ring band are locked at locating posts of an adjustment seat in the connection seat via through holes. The fixing effect of this kind of joining is not good so that other processing procedures must be matched, e.g., riveting the connection posts at the ring band. Therefore, the production cost is increased, and the manufacturing and assembling time is also increased. Additionally, the locating of the prior art adjuster can only be controlled by sense, resulting in inconvenient use. Furthermore, the adjuster has a large number of components, resulting in inconvenience in manufacturing and assembling. The present invention aims to resolve the above problems in the prior art.